EVOLUTION OF THE ARCTIC ALASKA-CHUKOTKA MICROPLATE FROM DETRITAL ZIRCON ANALYSIS OF CRETACEOUS SEDIMENTS OF THE NORTH SLOPE, ALASKA, AND JURA-CRETACEOUS PLUTONS AND SEDIMENTS OF CHUKOTKA, RUSSIA
The 110 to 95 Ma ages and Hf ratios (εHf = -14 to +4) of the youngest zircons in the Colville Basin match those of plutons in Chukotka that were emplaced during regional extension, uplift and erosion. Jurassic zircons in the Colville Basin and Chukotka Jura-Cretaceous clastic strata have a range of more evolved Hf ratios (εHf = -20 to +8) in contrast to the Hf ratios of Jurassic zircons derived from the erosion of the Angayucham terrane in the adjacent Brooks Range (εHf = +10 to +15). Specifically, the Hf ratios of 160 to 130 Ma zircons in Jurassic Chukotka clastic strata and the Colville strata are compatible with derivation from the Main and Northern plutonic belts of NE Russia, nearly 2,500 km to the west of the Colville Basin. Additionally, the presence of 550 to 400 Ma zircon in the Colville Basin requires the recycling of Triassic sediments from Chukotka/NE Russia, as previously reported. These findings suggest the bulk of the Aptian-Albian-Cenomanian sediment fill of the Colville Basin was derived from westward sources in Chukotka/NE Russia in a continental-scale sediment routing system. It is also possible that these paleogeographic linkages between source and sink may have been disrupted by the opening of the Amerasia Basin, or by the opening of the Canada Basin, after the deposition of the Torok and Nanushuk Formations.